The 7 MeV/u compact heavy ion cyclotron has been developed for HIMM injector at Institute of Modern Physics.The cyclotron was designed to operate at 31.02 MHz, with a final extraction energy of 7 MeV and beam current of10 A. The cyclotron RF system is an important part, which is required to provide cavity voltage up to 70 kV andcavity field control within 1% amplitude & 0:5? phase.